High speed accurate temperature measuring device

ABSTRACT

The present invention relates to a high speed accurate temperature measuring device especially useful for measuring human body temperature, comprising (a) an elongated temperature probe, (b) a first temperature sensor located beneath the surface of the probe, (c) at least one second temperature sensor located within the probe and parallel to the first sensor, (d) a thermal insulation member located between the first sensor and the second sensor (or sensors), (e) a data processing unit connected to the first and second temperature sensors calculating the body temperature according to heat flux measured between the body and the first sensor and between the first sensor and the second sensor (or sensors), and (f) a data display connected to the data processing unit.

FIELD OF THE INVENTION

The present invention generally relates to a high speed accuratetemperature measuring device which is especially useful for measuringthe temperature of a low thermal conductivity cavity hereinafter called“body” (e.g. human body). More specifically the present inventionrelates to a high speed accurate temperature measuring device whereinthe body temperature is calculated according to heat flux measuredbetween the body and a first temperature sensor location and between thefirst temperature sensor and a second temperature sensor (or sensors)location.

BACKGROUND OF THE INVENTION

Every temperature measuring process involves the transfer of heat fromthe measured body to the measuring device probe. Heat may be transferredin three ways; by conduction, by convection and by radiation. The methodof the present invention measures heat convection as well as heatconduction (such as in streaming air or liquids). Radiation heat meantlacks accuracy since achieving accuracy is dependent on earlierknowledge of constants that are not known with a high certainty.

Most temperature measuring devices using convection or conductionrequire the temperature measuring sensor to come into thermalequilibrium with the body being measure. When the body being measured isa poor heat conductor, the time to reach equilibrium (with thetemperature measuring sensor) may be considerable. This measurementwaiting time (to reach equilibrium) is a thermodynamic necessity.Various methods aiming at shortening this waiting time exist. Forexample DE 3527942 and U.S. Pat. No. 4,183,248 disclose a methodcomprising two temperature sensors and a heating elements. Shortening ofthis wait time is always at the expense of the accuracy of measurement.

The device of the present invention eliminates this waiting time.Instead of directly measuring the temperature (which requires waitingfor equilibrium), the device of the present invention calculates thetemperature by predicting temperature sensor measurements. Thisprediction relies on a heat transfer equation, and preferably a heatconduction equation whereby the body temperature is calculated accordingto heat flux measured (a) between the body and a first temperaturesensor and (b) between the first temperature sensor and a secondtemperature sensor (or sensors). Since firstly the heat fluxmeasurements do not require waiting for thermal equilibrium and secondlythe calculation per se is performed in real time on a standardmicro-processor, the device of the present invention can rapidly displaythe accurate temperature of the body.

Following is a detailed explanation of deriving the essential equations(embodied within the algorithm used by the data processing limitaccording to the present invention).

The Conduction Heat Transfer Equation (one dimensional without heatsources, since the heating body of the present device is not operatedduring the temperature measurement):${\rho \quad C_{P}} = {\frac{T}{t} = {\frac{- }{x}\left( {k\frac{T}{x}} \right)}}$

This equation represents heat flux differences between the inlet and theoutlet of the body under discussion.$\frac{T}{t} = {\frac{1}{\rho \quad C_{P}\Delta \quad x}{\Delta \left\lbrack {{k\frac{T}{x_{i\quad n}}} - {k\frac{T}{x_{out}}}} \right\rbrack}}$

where one dimensional heat flux (Q) is defined as the constant “k” timesthe change in temperature dT with regard to a change in position dx:${\left( {}^{*} \right)\quad Q} = {{- k}\frac{\Delta \quad T}{\Delta \quad X}}$

Using finite differences equation (*) can be written:$\frac{{T\left( {t + {\Delta \quad t}} \right)} - {T(t)}}{\Delta \quad t} = \begin{matrix}{\frac{1}{\rho \quad C_{P}\Delta \quad x}\left\lbrack {k\frac{{T\left( {x + {\Delta \quad x}} \right)} - {T(x)}}{\Delta \quad x}{_{x = x_{i\quad n}}{{- k}\frac{{T\left( {x + {\Delta \quad x}} \right)} - {T(x)}}{\Delta \quad x}}}_{x = x_{out}}} \right\rbrack}\end{matrix}$

If:$\omega_{i\quad n} = \frac{k\quad \Delta \quad t}{\rho \quad C_{P}\Delta \quad x_{i\quad n}^{2}}$

and$\omega_{out} = \frac{k\quad \Delta \quad t}{\rho \quad C_{p}\Delta \quad x_{out}^{2}}$

Then:${{\left( {}^{**} \right){T\left( {t + {\Delta \quad t}} \right)}} - {T(t)}_{{x} = {\frac{1}{2}{({x_{i\quad n} + x_{out}})}}}} = {{\omega_{i\quad n}\left\lbrack {{T\left( {x + {\Delta \quad x}} \right)} - {T(x)}} \right\rbrack}_{{x} = x_{i\quad n}} - {\omega_{out}\left\lbrack {{T\left( {x + {\Delta \quad x}} \right)} - {T(x)}} \right\rbrack}_{{x = x_{out}}}}$

If there are two heat sensors “S₁” which is located at x_(in) and “S₂”which is located at x_(out), and these sensors are separated by a finitedistance having a known thermal conduction coefficient (e.g a thermalinsulation member), and “S₁” is in thermal contact with the body, and“S₂” is within a thermal probe, and the body is located at x_(in)+Δxthen from (**) it is clearly seen that approximately:${{T\left( {t + {\Delta \quad t}} \right)} - {T(t)}_{{x} = {\frac{1}{2}{({x_{i\quad n} + x_{out}})}}}} = {{\omega_{i\quad n}\left\lbrack {T_{body} - T_{s_{1}}} \right\rbrack}_{} - {\omega_{out}\left\lbrack {T_{s_{1}} - T_{s_{2}}} \right\rbrack}}$

The temperature rise as evaluated at location ½(x_(in)+x_(out)) isdefined as heat in from the body ω_(in) times: [(T_(body)) minus (T_(s)₁ )] minus ω_(out) times heat out from the probe [(T_(s) ₁ ) minus (T₂ ₂)}.

The device of the present invention solves this equation for the unknownT_(body), ω_(in), ω_(out) according to measured temperaturesrepresenting the heat fluxes, without any need to wait for thermalequilibrium.

SUMMARY OF THE INVENTION

The present invention relates to a high speed accurate temperaturemeasuring device especially useful for measuring human body temperature,comprising (a) an elongated temperate probe, (b) a first temperaturesensor located beneath the surface of the probe, (c) at least one secondtemperature sensor located within the probe and parallel to the firstsensor, (d) a thermal insulation member located between the first sensorand the second sensor (or sensors), (e) a data processing unit connectedto the first and second temperature sensors calculating the bodytemperature according to heat flux measured between the body and thefirst sensor and between the first sensor and the second sensor (orsensors), and (f) a data display connected to the data processing unit.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a high speed accurate temperaturemeasuring device especially useful for measuring the human bodytemperature. The device of the present invention is likewise useful formeasuring animal body temperatures and for measuring the temperature ofany low thermal conductivity cavity.

The device of the present invention is comprised of:

(a) An elongated temperature probe. This probe is for insertion into abody cavity (in the present invention, the term “body cavity” alsorefers to the armpit; mouth cavity and rectum). The probe has a roundedinsertion tip to facilitate safe insertion into delicate body cavities.

(b) A first temperature sensor. This first sensor is located beneath thesurface of the probe near the insertion tip (to facilitate minimum depthinsertion).

(c) At least one second temperature sensor. This second sensor islocated within the probe and parallel to the fist sensor.

(d) A thermal insulation member. This member is located between the firssensor and the second sensor (or sensors). It should be emphasized (aswill be described) that the whole structure of the sensors andinsulation members is preferably rolled up.

(e) A data processing unit. This data processing unit is connected tothe first and second temperature sensors. The data processing unitcalculates the body temperature according to heat flux measured (i)between the body and the first sensor and (ii) between the fist sensorand the second sensor.

(f) A data display. This data display is connected to the dataprocessing unit, and is for displaying the body temperature ascalculated by the data processing unit The data display may alsoindicate messages (e.g. measurement error).

According to the preferred embodiment of the device of the presentinvention, a heating element located within the temperature probe. Thisheating element preheats the probe to a predetermined value, (and inmeasuring the human body temperature, to approximately 34 to 38° C.).When the probe is thus preheated, the time required for a high orderextrapolation of the measurements performed is shorter than would beotherwise the case using a room temperature probe (see heat transferequations described in Background section).

An optional additional second sensor (herein “third sensor”) can be usedby the data processing unit to improve the speed and accuracy of thetemperature measurement calculation. The third sensor is located withinthe (temperature) probe and parallel to the first sensor. The thirdsensor is likewise connected to the data processing unit. The dataprocessing unit can thereby in addition calculate the body temperatureaccording to heat flux measured between the first sensor and the thirdsensor.

The preheating step is optional but important since that by limiting therange of the temperature measured, the resolution is enhanced.

Furthermore, according to the preferred embodiment of the device of thepresent invention, the first sensor, the second sensor (or sensors), andthe heating element are photo-etched onto a single flexible substrate(printed circuit board). This substrate is then rolled or folded (so asto align the two sensors (or the three sensors) in parallel) with aninsulation member placed between the sensors. When rolled up, thesubstrate is the insulation intermediary itself. The thus alignedsensors (with their isolation intermediary) are inserted into theelongated probe and thereby held in alignment (so as to facilitate thetwo (or three) required flux measurements).

The elongated probe of the device of the present invention is made ofmetal or any other material with high thermal conductivity. The choiceof material for the elongated probe should also relate to sanitaryfactors of use, such as easy cleaning or sterilizing (in case of medicaluse).

The module comprising two (or three) sensors and a heating body has theadvantage of being cheaper, much easier to manufacture, does not requiremanual labor in manufacturing and does not require that the sensors betuned relatively to each other.

The present invention will be further described and clarified in detailby FIGS. 1-3 These figures are solely intended to illustrate thepreferred embodiment of the invention and are not intended to limit thescope of the invention in any manner.

FIG. 1 illustrates a schematic cross section of an inserted probe.

FIG. 2 illustrates an isometric cross section of the aligned sensors.

FIG. 3 is a flow chart of the operational procedures used in a highspeed accurate temperature measurement device.

FIG. 1 illustrates a schematic cross section of an inserted probe. Ametal cased temperature probe (1) inserted within a cavity of the humanbody (2) is shown. A three part assembly is comprised of a first sensor(3) separated from a second sensor (4) by a thermal insulation member(5). This three part assembly is located near the inserted tip of theprobe, wherein one side of the first sensor in thermal contact with themetal casing of the temperature probe, and with the second sensor nearthe axis of the probe. A heating (coil) element (6) is located withinthe insulation member. Furthermore the optional third sensor (7) isshown.

FIG. 2 illustrates an isometric cross second of the aligned sensors. Acurved three part assembly (of conformal shape to the curvature of theprobe in which it is to be inserted—see FIG. 1) is comprised of a fistsensor (3) (designated in the equation as “T_(s) ₁ ”) separated from aparallel second sensor (4) (designated in the equation as “T_(s) ₂ ”) bya the insulation member (5) of width “X”. Thus in the equationQ=k(dT/dX) (see background section) “dT” is equivalent to (T_(s) ₂−T_(s) ₁ ) or to T_(body)−T_(s) ₁ and “dX” is the final distance alongthe “X” axis.

The fist sensor is connected to the circuitry of the data processingunit (see FIG. 5) by electric contacts (8) and (9). The second sensor isconnected to the circuitry of the data processing unit (see FIG. 5) byelectric contact (10) and (11). The data processing unit (including anyrequired analog to digital conversion circuits, a power supply (e.g.battery) is in turn connected to a data display (see FIG. 5).

FIG. 3 is a flow chart of the operational procedures used in a highspeed accurate temperature measurement device. After the device isactivated a heating element within the probe, the heating elementpre-heats the probe to approximately 34 to 38° C. (in measuring thehuman body temperature) data readings are taken form the two sensors forapproximately 3 to 4 seconds (13), and from these measurements the dataprocessing unit calculate (14) the body temperature converged to aconstant range of ε limit. If the calculated body temperature convergedto a constant range of ε limit. If the calculated body temperature isnot within an acceptable range for body temperatures (15), thenadditional temperature measurements are taken from the two sensors forapproximately 0.5 seconds and the calculation step (14) is repeated. Ifthe calculated body temperature is within an acceptable range (16), thenthe calculated body temperature is displayed (17) on the data display.

The device according to the present invention has an analog and adigital circuits. The analog circuit's purpose is to sample temperatureand to activate the heating element. The circuit is connected to twosensors (with an option for a third sensor), a heating element and tothe digital circuit in order to relay the data samples and in order todigitally process the data. Each sensor has a separate circuit. Eachsensor's signal, arriving in a very low voltage (a total of 100 μV), isrelayed to a noise filter. The signals are then and are relayed to theanalog circuit segment's exit.

The digital circuit's purpose is to control the whole operation ofpre-heating and activating the analog segment, to produce measurements,to receive amplified and filtered signals from the analog circuitsegment, to convert them to binary (digital) values, to perform therequired mathematical calculations and to display the calculatedtemperature.

A multiplexer unit accepts the analog data from the analog circuit andserially passes it to be A/D convertor that quantifies the voltages tobinary (digital) values. The microprocessor calculates the temperatureand also controls the circuit's running of the program. This circuitsalso consists of a display unit and other circuit elements that supply astable electronic working environment for the microprocessor.

The data processing unit can now be attached to the appropriate electriccontacts. Then the substrate is rolled (or folded) so as to align thetwo sensors in parallel having an insulation member placed between thesensors. The thus aligned sensors with their insulation member areinserted into the elongated probe and thereby held in alignment. Thenthe data processing unit, data display, battery and appropriate holdersand connectors can be inserted into the region of the probe distant fromthe insertion tip, and the probe can be hermetically sealed forappropriate sanitary uses as a temperature measuring device especiallyuseful for measuring human body temperature.

What is claimed is:
 1. A high speed accurate temperature measuringdevice especially usefull for measuring human body temperature,comprising; a) an elongated temperature probe with a rounded insertiontip for insertion into a body cavity; b) a first temperature sensorlocated beneath the surface of the probe near the insertion tip; c) atleast one second temperature sensor located within the probe andparallel to the first sensor; d) a thermal insulation member locatedbetween the first sensor and the second sensor, e) a digital dataprocessing unit connected to the first and second temperature sensors;f) a data display connected to said data processing unit; wherein thedata processing unit calculates the body temperature by using thereadings from said temperature sensors and numerically solving the heattransfer equation based on the heat flux between the body and the firstsensor and between the first sensor and the second sensor.
 2. A deviceaccording to claim 1 having in addition a heating element located withinthe temperature probe, and said heating element is preheating the probeto a predetermined temperature and in measuring the human bodytemperature, to approximately 34 to 38° C.
 3. A device according toclaim 1 having a third sensor located within the probe and parallel tothe first sensor, said third sensor being connected to the dataprocessing unit, and said data processing unit in addition calculatingthe body temperature according to heat flux measured between the firstsensor and the third sensor.
 4. A device according to claim 1 whereinthe first sensor, the second sensor, and the heating element arephoto-etched onto a single flexible substrate.
 5. A device according toclaim 3 wherein the third sensor is photo-etched onto the flexiblesubstrate having the first sensor, the second sensor, and the heatingelement.
 6. A device according to claim 4 wherein the substrate isrolled or folded so as to align the two sensors in parallel having aninsulation member placed between said sensors, and the thus alignedsensors with their insulation intermediary are inserted into theelongated probe and thereby held in alignment.
 7. A device according toclaim 1 wherein the elongated probe is made of metal or other similarmaterials good for thermal heat conduction.